Structure and Rotation Mechanism of Brushed DC Motors
Brushed DC motors are one of the most widely used electric machines in everyday appliances, toys, and industrial tools. Their simple design, low cost, and ability to deliver high torque at startup make them indispensable in many applications. In this article, we will explore the structure of brushed DC motors and the mechanism that enables their rotation, providing both beginners and professionals with a clear understanding of how these motors operate.
Darren Yi
sales@zmartechome.com
1. Introduction to Brushed DC Motors
A brushed DC motor is an electromechanical device that converts direct electrical energy into rotational mechanical motion. Unlike brushless DC motors (BLDC), brushed motors use a mechanical commutation system involving brushes and a commutator to control the direction of current within the motor's armature.
These motors are popular in:
- Household appliances - blenders, hair dryers, vacuum cleaners.
- Automotive systems - windshield wipers, power seats, window regulators.
- Industrial tools - drills, conveyors, small pumps.
- Toys and hobby projects - RC cars, robotics kits, model airplanes.
To understand why they are so versatile, let's break down their structural elements.
2. Structural Components of a Brushed DC Motor
The basic structure of a brushed DC motor can be divided into four main parts:
2.1 Magnetic Field (Stator)
The stator provides the fixed magnetic field necessary for motor operation.
- In small DC motors, the field is created by permanent magnets.
- In larger industrial motors, the stator may use electromagnets (field windings) to generate a stronger magnetic field.
This magnetic field interacts with the armature’s field to produce motion.
2.2 Armature (Rotor)
The armature, also called the rotor, is the rotating part of the motor. It contains copper windings wound around an iron core.
When current passes through these windings, they generate a magnetic field that interacts with the stator’s field, creating torque.
2.3 Commutator
The commutator is a cylindrical assembly of copper segments attached to the armature.
It works as a mechanical switch that reverses the direction of current in the armature coils at the right time, ensuring continuous rotation.
2.4 Carbon Brushes
Carbon brushes press against the commutator and serve as the electrical connection between the external power source and the armature windings.
As the rotor turns, the brushes maintain sliding contact, allowing current to flow seamlessly.
3. Rotation Mechanism of a Brushed DC Motor
The rotation of a brushed DC motor is based on electromagnetic principles—specifically the interaction of a magnetic field and electric current.
(1) Current Flow
When a DC voltage is applied, current flows from the power supply into the brushes, through the commutator, and into the armature windings.
(2) Magnetic Interaction
The energized armature coils act like an electromagnet. The N (north) and S (south) poles of the armature interact with the stator’s fixed magnetic field.
- Like poles repel each other.
- Opposite poles attract each other.
This push-and-pull creates torque on the rotor.
(3) Commutation
As the rotor moves, the commutator switches the current direction in the armature windings. This ensures that the torque always acts in a consistent rotational direction, preventing the rotor from stopping at dead positions.
(4) Continuous Rotation
The repeated process of attraction, repulsion, and commutation results in smooth, continuous rotation of the armature.
4. Types of Brushed DC Motor Structures
Brushed DC motors can be categorized based on the number of poles in the armature:
- 2-pole motors – Simple design, often used in small devices.
- 3-pole motors – Common in toys and hobby motors (such as RC cars).
- Multi-pole motors (7–9 poles or more) – Used in industrial applications for smoother torque and better performance.
5. Advantages of the Brushed DC Motor Structure
The structure and rotation mechanism of brushed DC motors bring several benefits:
- Simplicity – Fewer components compared to brushless systems.
- High starting torque – Ideal for loads that need instant acceleration.
- Low cost – Economical to produce and repair.
- Easy control – Speed is easily adjusted by changing the supply voltage.
6. Limitations of the Brushed Design
While brushed DC motors are widely used, their structure introduces some challenges:
- Brush wear – Carbon brushes degrade over time and require replacement.
- Electrical noise – Sparking at the commutator can generate interference.
- Efficiency loss – Friction and electrical resistance reduce efficiency.
- Maintenance requirements – More frequent servicing compared to brushless motors.
7. Conclusion
The structure and rotation mechanism of brushed DC motors make them a reliable, cost-effective, and simple choice for many applications.
By combining a stator for the magnetic field, a rotor (armature) with windings, a commutator, and carbon brushes, these motors convert electrical energy into rotational motion using straightforward electromagnetic principles.
Although brushless DC motors are gaining popularity in modern energy-efficient systems, brushed motors remain relevant in appliances, automotive components, and hobby projects due to their affordability, availability, and ease of use.
For engineers, hobbyists, or product designers, understanding the internal structure and rotation mechanism of brushed DC motors provides valuable insight into motor technology and helps in selecting the right motor for a given application.
